This invention relates generally to the bleaching and sanitizing of fabrics and, more specifically, relates to compositions and methods for effecting such operations with reduced degradation to the fabric and/or dyes contained in the fabrics.
It has long been known in the prior art to bleach and/or sanitize fabrics with various chemical compounds which, in aqueous solution, provide a source of available chlorine. The said available chlorine is normally present in solution as hypochlorous acid or hypochlorite ion, depending upon the pH of the solution.
Among the compounds useful for such purposes are the dihalohydantions. Typical dihalohydantoins include 1,3-dichloro- 5,5-dimethylhydantoin and 1-bromo-3-chloro-5, 5-dimethylhydantoin.
In practical use, however, these compounds have the potential to cause extensive damage to the substrates which are being bleached or sanitized, unless they are used according to a prescribed method. This prescribed method of use normally dictates a set of use conditions which eliminate the possibility of the compounds coming in contact with the substrate while in the concentrated form. For example, in the bleaching or sanitization of laundry, normally performed in a washing machine, according to the usually prescribed method of use, the compounds must be dissolved in the wash water prior to the addition of fabrics to guard against the contact of undissolved or partially dissolved particles of the bleaching compound with the fabric being laundered. This is a marked inconvenience, and requires the constant supervision of the operator to insure that no fabric damage occurs. Should the dihalohydantoins, or formulations containing them, be poured directly onto wet fabrics in the machine under conditions of misuse, extensive damage will occur--in the form of severe dye destruction and/or fabric pinholeing.
In an effort to overcome the damage which thus occurs through the normally expected "misuse" of this type of product, formulators have gone to great lengths to encapsulate the dihalohydantoins, through the use of water soluble coatings, or agglomeration techniques, in an effort to prevent the direct contact of these compounds with the fabric. These methods are expensive, and, at best, only partially prevent the damage which invariably occurs with misuse. The problem of formulating a dry chlorine bleach practical for home use has been the subject of considerable research and has been a long-standing problem in the industry. Although many attempts at commercialization have been made, no successful widely marketed product bearing the necessary attributes currently exists.
The use of the aforementioned dihalohydantoins (DHH) as bleaching agents is disclosed, inter alia, in U.S. Pat. No. 4,713,079 to Chun et al which thus describes the use of these compounds in bleaching particles containing, along with the DHH, a buffering salt and an organic binder. Although these formulations offer a lower damage potential than DHH alone, the compositions taught have the potential to cause significant fabric and dye damage when used, as might be expected, in conjunction with a normally alkaline laundry detergent product, since the combination of the materials under misuse conditions can result in a local pH which is high enough to allow the DHH to cause fabric and dye damage. Additionally, the necessity of adding an organic binder to the compositions complicates the manufacturing process and serves, at an additional expense, only a mechanical function.
Ouinn, U.S. Pat. No. 2,795,556 teaches the production of bleaching compounds based upon dichloro-dimethyl hydantoin, through spray drying processes, which are buffered to a pH range of 6-10. This pH range is high enough to cause significant fabric and dye damage under conditions of misuse.
Wearn et al, U.S. Pat. No. 3,257,324 describes a dichloro-dimethylhydantoin bleach which has an aqueous pH of at least 7.5. Misuse damage potential is not addressed, and would most certainly occur.
Zetterouist et al, U.S. Pat. No. 4,167,832 teaches the use of dichloro-dimethylhydantoin in an application for preserving flowers, whereby it is used as a source of chlorine to prevent bacteria formation in the vase water. It is disclosed that the dichloro-dimethylhydantoin splits off chlorine at an increasing rate as the pH of the water falls from a value of 6.8. This is contrary to the findings of the present invention.
In accordance with the foregoing, it may be regarded as an object of the present invention, to provide a composition for use in aqueous solution in the bleaching and sanitizing of fabrics, which, under conditions of misuse, will cause little or no damage to the fabric being treated.
It is a further object of the invention, to provide a method for manufacture of compositions of the foregoing character, which readily produces such compositions in a highly utilitarian pelletized or granulated form; and which can effect such result without the use of organic binders.